No two businesses are the same, and no two businesses' needs and environments are the same. Fortunately, there's considerable flexibility when it comes to virtualization. Windows 7 supports several alternative deployment models for virtual desktops.

VDI or Centralized Virtual DesktopsVirtual Desktop Infrastructure (VDI) is one such alternative desktop deployment model for Windows 7. Instead of running a local copy on each user's desktop, you create and store a common image on one or more servers in the datacenter. You then deploy this image to a server running a hypervisor.

There are several benefits to implementing a VDI:

You can rapidly deploy a common supported desktop environment by creating a single Windows 7 desktop image. Use that image to deploy virtual machines (VMs) on your server hypervisor. In that way, a single server can support many virtual desktops. Each of these desktops reacts as a standalone Windows 7 desktop. Unlike using Remote Desktop Services (RDS), the users connecting to a virtual desktop can have full access to all features of that VM without impacting the other virtual desktops or the host server. Your users could still use the Remote Desktop Connection client to connect to their virtual desktop.

You can make centralized updates and changes to Windows 7 by updating the desktop image, then redeploying that updated image to all your users. The next time they log on, they'll have the updated image with the rest of their settings maintained.

If there's a problem with an update that requires a rollback to a previous version of the desktop image, you can do that quickly and easily. Save a copy of the previous image before performing the update. That way, you can roll back by redeploying the previous image if needed. When your users log off and log back on, they'll receive the previous image. There are some barriers to implementing a VDI. The start-up costs can be high, and the return on investment is longer than on a server virtualization project. This is a business decision that you shouldn't take lightly. Plan and establish a budget before embarking on the project. Here are some specific areas you need to consider:

VDI may not reduce desktop costs because any savings are typically redirected into server, network and storage infrastructure. You will have to make improvements in desktop management and user management to support large numbers of virtual desktops. Applying Group Policy settings through Active Directory to redirect user folders and implementing roaming profiles will increase the flexibility of a VDI design. Consider VDI when desktop flexibility is more important than immediate cost savings.

A user connected to a virtual desktop requires a constant network connection. Whether this is through a Local Area Network, across a Wide Area Network (WAN) or a remote connection, the user must be connected to the virtual desktop to be productive. If a user must be able to operate in a disconnected environment, VDI won't be a suitable solution. If your users are not mobile or only work when they're connected to the network, this could be a viable solution.

Planning your VDI deployment is critical to the project's success because it can be complex. It's also a significant infrastructure investment. Defining which users will benefit the most and outlining the requisite virtualization components is crucial for success.

Distributed Virtual DesktopsA distributed desktop model lets you deploy different desktop images to a specific group of users based on their location or job function. This model can be useful if you have a number of different types of users in a single location or users in a variety of locations such as branch offices. Each group will have different desktop requirements or might be connected by slow or intermittent links. The remote users may have a file server that stores their files and information.

Another distributed desktop design could include setting up a pre-execution environment. This method lets you deploy an image to a server with a desktop to download and boot at startup. You can develop and assign several desktop images. When a user starts up his desktop, the image is streamed to the device. Changing a desktop image is as simple as reconfiguring the device's target image and restarting the desktop.

This is a viable design if you must run applications from the local desktop. Some applications require a hardware dongle or a specific Media Access Control address for licensing. Applications that require special graphics or additional cards or adapters not supported within a virtual environment are also good candidates for this type of deployment.

The drawbacks and benefits are as follows:

You must load the individual images with any applications or drivers required for your desktops. Unless all desktops are identical, you might need to add different drivers for each type of hardware for which you're preparing the image.

You can configure a different image to load on a desktop as a shift changes or new updates are configured. This is particularly useful because a new image is loaded each time the desktop is rebooted. Viruses and malware are limited in their effectiveness because the entire desktop image is reloaded each time the desktop is reloaded.

The VDI image is received from the primary datacenter. The management station controls which images are assigned to local and remote users. Local users connect to the image they're assigned from the VDI server in the datacenter.

Therefore, this model is best used with a local server that holds the desktop images. Loading a desktop image over a WAN is a slow process that will discourage remote users from rebooting their desktops. In this scenario, consider using either a local VDI or a distributed VDI solution.

You can also distribute desktops using Microsoft System Center Configuration Manager. You can use this to distribute both applications and desktops to user's desktops, both local and remote. This model will actually install the desktop OS on the targeted desktop. This is a fairly complex process, so you'll have to plan and test the solution for optimum success. You can also use this management solution in conjunction with System Center Virtual Machine Manager 2008 to create, deploy and manage desktops in a distributed environment.

When it comes to deploying a user's desktop, there are several options. One design rarely fits all situations. You can see from these different scenarios that you can also use a combination of all these options to meet your specific needs.